Yes, D+ were allowed in the suite lounge. It was called the concierge lounge -- and it was for full suites (not JS) Diamond + and Pinnacle. I don’t mind that they excluded us, just wished they told us, so we were not embarrassed when our cards did not open the door. I guess RCL thought the change of name was enough notice.
We are on the Navigator. With the new renovations, they eliminated the Concierge lounge on deck 9 and opened a Suite lounge on deck 14. Diamond plus not allowed in the Suite lounge and when asked about our “eviction” the staff refuses to acknowledge that this is the case. A rose by any other name is not a rose in RCCL language.